The present invention relates broadly to footwear and is more particularly concerned with a shoe having disposed therewithin an orthotic cradle device.
In human locomotion the foot undergoes a highly complex and continuously changing series of motions, vectors and loads. The gait cycle of a human is generally considered as comprising two distinct phases: (a) the stance phase, and (b) the swing phase. The beginning of the stance phase is signalled by the heel strike of the foot against the support surface. At this point of the cycle the foot begins to become loaded with body weight and, in response, pronates, thereby to result in a lowering of the medial longitudinal arch, an outward turning of the foot and an inward rotation of the leg. During this pronation of the foot, the bony articulations or joints of the mid and hind foot loosen somewhat in order that the foot can both adjust to the support surface and absorb the mechanical shock of heel strike and weight bearing. As the plantar surface of foot rolls proximo-distally onto the support surface, and at some point subsequent to midstance, the heel begins to invert and the foot begins to resupinate. At this juncture of the stance phase the forefoot is fixed to the support surface with the heel in inversion, the heads of the first and fifth metatarsals are splayed apart and the foot is in a rigid structural condition and, ideally, in a neutral, that is to say, neither pronated nor supinated, position. Next, plantar-flexion of the foot begins, the arch becomes rigid and the heel lifts off the support surface, usually with accompanying further supination. The plantar fascia shortens and the toes begin to flex, creating a so-called "windlass effect" whereby the arch is elevated and which constitutes the final or "propulsive" segment of the stance phase immediately preceding the beginning of the swing phase of the gait cycle and the heel strike of the opposite foot. In the normal swing phase, during which the foot is lifted entirely off the support surface and, therefore, is in a non-weight bearing condition, the normal foot returns from its supinated position to a neutral position, as do the articulations of the fore, mid and hind foot, in preparation for the onset of its next stance or weight bearing phase.
Flexible biomechanical deformities and anomalies of the foot tend to decrease the foot's intrinsic resistance to weight bearing and environmental forces. Where this scenario is present, there is usually presented a predisposition of the medial longitudinal arch and the subtalar joint to excessive triplanar motion or pronation which can generally be observed by careful visual analysis of the gait cycle. Thus, the joint excursions involved in pronation of the foot which, as mentioned above, is a normal motion in the early portion of the stance phase can themselves be dimensionally excessive and/or the foot can fail to properly return from its pronated state to a fully neutral position in preparation for the onset of the propulsive segment of the stance phase. Accordingly, if left unresolved, these structurally destabilizing forces acting upon a biomechanically unsound foot result in hypermobility syndromes of the first and fifth metatarsals, plantar flexion and medial deviation of the talar head, as well as naviculo-cuneiform sag. Such hypermobility syndromes constitute forerunners to many multi-focal sub-acute, acute and chronic pathologies of the foot, including such conditions as hallux-abducto-valgus deformity, tailor's bunion, hellomata, degenerative joint disease, plantar fascial strain, heel spur syndrome, subluxation of the calcaneal-cuboid joint and lateral foot column problems. Such pathological foot conditions, particularly because they generally cause the sufferer thereof to compensate for foot pain or deformity by altering his or her gait, can also foster or exacerbate pathologies relating to portions of the human anatomy other than the foot, such as ankle, knee, hip and spine.
In view of the foregoing potential or actual problems associated with the hypermobile foot, orthotic devices have been developed which are said to stabilize the foot in order to prevent excessive pronation and/or to maintain the foot in an anatomically correct position within footwear during the gait cycle. Amongst these are various mid-hind foot stabilizing strap arrangements disclosed by R. Stephen Curtis in U.S. Pat. No. 4,461,288, issued Jul. 24, 1984 and U.S. Pat. No. 4,649,939, issued Mar. 17, 1987. Said strap arrangements are disclosed to be worn external to the shoe and are said to stabilize motion of the infratalar joints and prevent slippage of the foot within the shoe. These strap arrangements broadly comprise a dorsal strap, an Achilles strap and a plantar strap, said straps being joined together at one end to form a generally Y-shaped arrangement. The plantar strap is disposed under or through the sole, proximate the plantar fascia, the dorsal strap disposed over the instep and the Achilles strap disposed around the heel of the shoe, the free ends of the dorsal and Achilles straps comprising clasps such that their lengths may be adjusted while securing them under tension to the other end of the plantar strap. The completed construction defines an adjustable mid and hind foot-encircling retention harness disposed over the exterior of the shoe which, acting indirectly upon the foot through the shoe, is said to stabilize the bony articulations of the foot, particularly along the infratalar joints, thereby to prevent or mitigate against excessive pronation thereof, and to secure the foot within the shoe so as to avoid or minimize slippage of the foot within the shoe and to thereby avoid the loss of arch support by the shoe which is said to result as a result of such slippage. Apparently, the Curtis stabilizer requires the use of relatively unyielding and inelastic strapping materials, such as cotton polyester blend webbing, for its construction because, inter alia, patentee states that periodic readjustment of the straps may be required in order to accomodate the swelling of the foot which often occurs during the course of an exercise routine. Also indicative of the use of unyielding inelastic strapping materials in the construction of the Curtis stabilizers is the patentee's express intention that a force applied to any one of the straps be distributed to the remaining straps of the construction.
In accordance with the present invention there is provided a shoe comprising an internal orthotic cradle device which, unlike the external retention harnesses disclosed in the foregoing Curtis patents, interacts dynamically and both directly and indirectly upon the plantar anatomy of the foot.